Writing instrument



FIG. 1 is a lower front left perspective view of a writing instrument showing our new design;

FIG. 2 is an upper right perspective view thereof;

FIG. 3 is a left side elevation view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a front elevation view thereof;

FIG. 6 is a right side elevation view thereof;

FIG. 7 is a top plan view thereof; and,

FIG. 8 is a rear elevation view thereof. 

The ornamental design for a writing instrument, as shown and described. 